On e.g. https://docs.arduino.cc/language-reference/en/variables/utilities/PROGMEM/ there is a link to the github at the bottom:
The content on docs.arduino.cc is facilitated through a public GitHub repository. If you see anything wrong, you can edit this page here.
But it does not point to this repo, but not (anymore?) existing https://github.com/arduino/docs-content-reference
This link does not seem to exist in this repo, but figured it would be an appropriate enough place to report it anyway.